Machine to machine (Machine to Machine, M2M) communication, called machine type communication (Machine Type Communication, MTC) as well, is a technology which does not need human intervention and in which machine and machine communicate with each other directly. The MTC has features of a huge number of devices, low mobility, and small communication flow of a single device and so on. Only a signalling plane bearer is established between an MTC device and a network side entity. Through the signalling plane bearer, data is carried in control signalling to be transmitted.
In the prior art, after a communication between an MTC device and a network side entity is over, the MTC device and the network side entity might delete security context which is used for protecting security of data transmission, such that when the MTC device and the network side entity transmit data by control signalling at a next time, security protection of the data may not be performed since there is no security context, and the data of the MTC device cannot be transmitted safely.